Artikel Jurnal
Easton, David, author
Prentice-Hall, 1965
Buku Teks
Lasswell, Harold D.
Routledge & Kegan Paul Ltd., 1949
Buku Teks
Sargent, Lyman Tower, author
Cole Publishing, 1990
Buku Teks
Sargent, Lyman Tower, author
The Dorsey Press, 1981
Buku Teks